• Proceedings of the Korea Concrete Institute Conference
• /
• 1999.10a
• /
• pp.29-46
• /
• 1999

The performance based design obligates quantitative assessment of required performances by means of transparent and objective science. In this design scheme, simulation of both macro and micro-scale structural behaviors is thought to be a powerful tool. This paper proposes a way how to unify the structural safety and serviceability check method and durability assessment of RC structures. Though component chemical-physical processes are crudely assumed, system dynamics of micro-scale pore structure formation and macro-scale defects and deformation of structures was shown as possible and promising approach in future. The authors understand that the unification of structural and durability design has just started. For further progress and development, predictive tool of structural behaviors from birth to death of concrete under any specified environment and load serves as an essential technicality.

• Journal of Advanced Marine Engineering and Technology
• /
• v.15 no.5
• /
• pp.30-37
• /
• 1991

Steam ejector systems are widely used for the evacuation systems because of their high working confidence and simlicity. And recently these are used as the thermo-compressors in various energy saving systems. In this practical experiment, we have obtained the results as follows : (1) The velocity coefficient of the motive steam nozzle was 0.92-0.98. (2) The optimal area ratio was 0.00625 at pressure ratio 5.2 and expansion ratio 101.3. (3) The performance and efficiency of the steam ejector were mainly affected by the axial position of nozzle. (4) The good performance of the domestic manufactured steam ejector was confirmed in comparison with the foreign one. And by experimental results, we have carried out the improvement of Computer Aided Design Program of steam ejector which will be helpful for systematic research into the steam ejector.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.24 no.2
• /
• pp.196-203
• /
• 2012

Energy foundations and other thermo-active ground structure, energy wells, energy-slab, and pavement heating and cooling represent an innovative technology that contributes to environmental protection and provides substantial long-term cost savings and minimized maintenance. This paper focuses on earth-contact concrete elements that are already required for structural reasons, but which simultaneously work as heat exchangers. Pipes, energy slabs, filled with a heat carrier fluid are installed under conventional structural elements, forming the primary circuit of a geothermal energy system. The natural ground temperature is used as a heat source in winter and a heat sink in summer. The geothermal heat pump system with energy-slab represented very high heating and cooling performance due to the stability of EWT from energy slab. However, the performance of it seemed to be affected by the atmospheric air temperature.

• Smart Structures and Systems
• /
• v.26 no.6
• /
• pp.703-720
• /
• 2020

This paper investigates the safety of the wind turbine blade against excessive deformation. For this purpose, the performance of the blade in the along-wind direction is improved by longitudinal stiffener made of shape memory alloy. The rationale behind the selection of this smart material is due to its ability to offer excellent thermo-mechanical behaviour at low strain. Here, Liang-Roger model is adopted for vibration control, and the super-elastic effects are utilised for blade stiffening. Turbulent wind fields are generated at the hub height using TurbSim and the corresponding loads are evaluated using blade element momentum theory. An efficient switching algorithm is developed along with performance curves that enable the designer to select an optimal mode of heating depending upon the operational scenario. Numerical results presented in this paper clearly demonstrate the performance envelope of the proposed stiffener and its influence on the reliability of the blade.

• KIEAE Journal
• /
• v.14 no.3
• /
• pp.79-86
• /
• 2014

Studies have shown that the thermal performance of buildings changes depending on the year of construction completion. It leads to increased energy consumption of buildings and significant financial burden on users. Thus, this study has calculated the thermal insulation performance of 86 apartments quantitatively, using temperature difference ratio and sensible heat flux. Also, energy consumption characteristics depending on the year of construction completion and thermal insulation performance were analyzed by comparatively analyzing the results of insulation performance evaluation and heating costs. The analysis results are as follows. As for thermal insulation performance, it was around 70% lower in the apartments completed before 1985, compared to apartments completed after 2010. As for heating costs, the apartments with the highest heating cost incurred 1.5 higher heating cost than the apartment with the lowest heating cost. In terms of the insulation performance evaluation, the difference was 2.5-fold.

• Tunnel and Underground Space
• /
• v.30 no.5
• /
• pp.446-461
• /
• 2020

Numerical simulations of CIEMAT column test in Spain are performed to investigate the coupled thermo-hydro-mechanical (THM) behavior of MX80 bentonite pellets using TOUGH2-FLAC3D. The heater power and injection pressure of water in the numerical simulations are identical to those in the laboratory test. To investigate the applicability of the thermo-hydraulic (TH) model used in TOUGH2 code to prediction of the coupled TH behavior, the simulation results are compared with the observations of temperature and relative humidity with time. The tendencies of the coupled behavior observed in the test are well represented by the numerical models and the simulator in terms of temperature and relative humidity evolutions. Moreover, the performance of the models for the reproduction and prediction of the coupled TH behavior is globally satisfactory compared with the observations. However, the calculated stress change is relatively small and slow due to the limitations of the simple elastic and swelling pressure model used in numerical simulations. It seems that the two models are insufficient to realistically reproduce the complex coupled THM behavior in the bentonite pellets.

• Journal of Advanced Marine Engineering and Technology
• /
• v.39 no.4
• /
• pp.425-431
• /
• 2015

LNG (liquefied natural gas) is considered the best alternative eco-fuel, and many studies on the LNG fuel system have been performed to use LNG as the fuel for ships. For the LNG fuel supply system, natural gas transfers from the vaporizer to the engine in the gaseous state with a temperature of $50^{\circ}C$ and a pressure of 35MPa. Therefore, a structural safety evaluation of the double-walled pipelines considering thermal load is essential. In this article, an uniaxial tensile test for super duplex stainless steel, material for double-walled pipe, according to the annealing time was carried out to analyze the thermal effect. In addition, thermo-structural analysis of the high temperature-high pressure double-walled pipe with fixed supports that are now used widely was carried out to evaluate the structural safety. To minimize stress concentration of the connection point between the support and inner pipe, the shapes of the new type support that can slip through inner pipe were proposed, and the supports which has best structural performance was selected using the results from the thermo-structural analyses of new supports and an analysis of the whole double-walled pipeline was performed to ensure structural safety. These results can be used as a database for the design of double-walled pipelines and sliding support.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.21 no.2
• /
• pp.48-59
• /
• 2017

In this study, an analysis of the thermo-fluid dynamic and missile-motion performance was carried out through a numerical simulation inside the missile canister. Calculation was made in an analytical volume using dynamic grid and evaporated water was used as a coolant. To analyze the interaction among the hot gas, coolant, and mixture flow, Realizable $k-{\varepsilon}$ turbulence and VOF (Volume Of Fluid) model were chosen and a parametric study was performed with the change of coolant flow rate. As a result of the analysis, pressure of the canister showed a large difference depending on the presence or absence of the coolant, and also showed a dependancy on the amount of coolant. Velocity and acceleration were dependent on the canister pressure.

• Korean Chemical Engineering Research
• /
• v.54 no.4
• /
• pp.479-486
• /
• 2016

The efficient steam drum should be required to reduce carbon oxide emissions and heat recovery in oxygen converter hood system. However, steam generation is limited to the time of the oxygen blowing period, which is intermittent or cyclical in operation of steel-making process. Thus, steam drum should be optimized for an effective steam generation during the oxygen blowing portion of the converter cycle. In this study, a three-dimensional computational fluid dynamics (CFD) model has been developed to describe the impacts of changing various operating conditions and geometric shape on thermo-fluid characteristics and performance of the steam drum. This model encompasses not only fluid flow and heat transfer but also evaporation and condensation at the interfacial surface in the steam drum by using VOF (Volume of Fluid) method. To validate the prediction performance of this model, comparison of the steam flow rate between numerical and experimental result has been performed, resulting in the accuracy of the relative error by less than 3.2%.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.38 no.6
• /
• pp.596-604
• /
• 2010

In order to investigate the operating conditions and major design parameters of a dual ramjet propulsion system, an theoretical analysis of ramjet and scramjet propulsion systems was performed. The performance characteristics of each engine are delivered by thermo-dynamical cycle analysis, considering loss effects in a real engine. The performance sensitivity analysis is conducted by investigating various performance parameters, such as an intake efficiency, combustor inlet Mach number, configuration of the combustor, fuel flow rate, and exhaust nozzle efficiency. Based on these analysis results, the processes of application to dual ramjet cycle engines are specified.